Dates: AD 294-310The Argenteus DenominationAn illustrated discussion of the history and types of the denomination.
This coin: 20-19 mm. An argenteus of Diocletian, struck 96 (XCVI) to the pound of silver.

Dates: Roman Republic and Empire to AD 321TheQuinariusDenominationAn illustrated discussion of the five time periods with the "quinarius"
This coin: 16-15 mm. Issue of the moneyer C. Fundanius, 101 BC.

Dates: AD 287-297Usurpers who wanted to join the clubUsurpers under the first tetrarchy (the time of Diocletian and Maximian)
This coin: The usurper Domitius Domitianus at Alexandria, Egypt

Dates: Third to First Centuries BCRoman Republican Coin Types and their DatingRepublican coins are not explicitly dated, so how can we know their dates?A timeline page of examples and a page of theory.
This coin: one of the first types of the silver "denarius" denomination

Date: 425-1071 Byzantine Coins of Cherson (Kherson)
The unusual Byzantine types from the city of Cherson in the Crimea in Ukraine.
A resource for collectors.
This coin: The "H" (= 8) pentanummia denomination.

Date: 306-310Constantine as Caesar and as FIL AVG (A.D. 306-310)An illustrated article on the the Roman rulers and their mints from 306-310
when Constantine was awarded the unusual title "Filius Augusti".This coin: Constantine as "FIL AVG", minted at Antioch.

Date: 289-290 Officina Marks of the Roman emperors
Diocletian and Maximian at Siscia (289-290 AD)
The unique use of the Jovian and Herculian titles to indicate officina numbers
This coin: Maximian with mintmark incorporating ΛI, part of a code.

Date: 305-306 The unusual "quarter-follis" denomination struck 305-306 AD under the tetrarchyAn illustrated list of all the varieties. An educational resource for collectors.
This coin: A quarter-follis of Maximinus II.

Date: 330-340 CONSTANTINOPOLIS:Roman coins commemorating
the founding of Constantinople under Constantine.
A short article here (only about this one common type).
A complete list and longer article here. (The picture links to this one.)
This coin: CONSTANTINOPOLIS/Victory, 330-340 AD.